Skip to contents

Cards are a common organizing unit for modern user interfaces (UI). At their core, they’re just rectangular containers with borders and padding. However, when utilized properly to group related information, they help users better digest, engage, and navigate through content. This is why most successful dashboard/UI frameworks make cards a core feature of their component library. This article provides an overview of the API that bslib provides to create Bootstrap cards.

Setup code

To demonstrate that bslib cards work outside of Shiny (i.e., in R Markdown, static HTML, etc), we’ll make repeated use of statically rendered htmlwidgets like plotly and leaflet. Here’s some code to create those widgets:

library(bslib)
library(shiny)
library(htmltools)
library(plotly)
library(leaflet)

plotly_widget <- plot_ly(x = diamonds$cut) %>%
  config(displayModeBar = FALSE) %>%
  layout(margin = list(t = 0, b = 0, l = 0, r = 0))

leaflet_widget <- leafletOptions(attributionControl = FALSE) %>%
  leaflet(options = .) %>%
  addTiles()

Shiny usage

Cards work equally well in Shiny. In the examples below, replace plotly_widget with plotlyOutput() and leaflet_widget with leafletOutput() to adapt them for Shiny server-rendered plots/maps.

Hello card()

A card() is designed to handle any number of “known” card items (e.g., card_header(), card_body(), etc) as unnamed arguments (i.e., children). As we’ll see shortly, card() also has some useful named arguments (e.g., full_screen, height, etc).

At their core, card() and card items are just an HTML div() with a special Bootstrap class, so you can use Bootstrap’s utility classes to customize things like colors, text, borders, etc.

card(
  card_header(
    class = "bg-dark",
    "A header"
  ),
  card_body(
    markdown("Some text with a [link](https://github.com)")
  )
)
A header

Some text with a link

Implicit card_body()

If you find yourself using card_body() without changing any of its defaults, consider dropping it altogether since any direct children of card() that aren’t “known” card() items, are wrapped together into an implicit card_body() call.1 For example, the code to the right generates HTML that is identical to the previous example:

card(
  card_header(
    class = "bg-dark",
    "A header"
  ),
  markdown("Some text with a [link](https://github.com).")
)
A header

Some text with a link.

Restricting growth

By default, a card()’s size grows to accommodate the size of its contents. Thus, if a card_body() contains a large amount of text, tables, etc., you may want to specify a height or max_height. That said, when laying out multiple cards, it’s likely best not to specify height on the card(), and instead, let the layout determine the height layout_column_wrap().

Although scrolling is convenient for reducing the amount of space required to park lots of content, it can also be a nuisance to the user. To help reduce the need for scrolling, consider pairing scrolling with full_screen = TRUE (which adds an icon to expand the card’s size to the browser window). Notice how, when the card is expanded to full-screen, max_height/height won’t effect the full-screen size of the card.

card(
  max_height = 250,
  full_screen = TRUE,
  card_header(
    "A long, scrolling, description"
  ),
  lorem::ipsum(paragraphs = 3, sentences = 5)
)
A long, scrolling, description

Ipsum feugiat fusce ornare dictum velit feugiat congue vitae. Faucibus mollis ante fermentum: semper tristique praesent litora elementum. Diam nascetur curae quam nibh mus, posuere aliquet fermentum vestibulum at mattis! Curabitur euismod porttitor nascetur posuere lectus quam risus massa, facilisis erat. Quam mauris vehicula integer vitae!

Sit suspendisse donec neque viverra ultricies diam in. Curabitur tortor diam praesent est lectus ornare? Netus proin neque velit interdum, cubilia nostra suscipit sociosqu. Hac sagittis non dignissim erat, enim: vehicula volutpat nibh sollicitudin felis ac? Vitae ac sociosqu curae rhoncus quis – ornare, turpis, sociosqu dictumst, nam per.

Amet faucibus sodales mus, risus orci lobortis leo! Eleifend platea senectus erat, libero: quisque interdum risus. Bibendum ad ac non urna vestibulum aptent mus, nam quis sollicitudin? Natoque est parturient, laoreet eleifend integer turpis id conubia torquent eu. Enim interdum cras neque commodo consequat in facilisi magnis sem neque.

Filling outputs

A card()’s default behavior is optimized for facilitating filling layouts. More specifically, if a fill item (e.g., plotly_widget), appears as a direct child of a card_body(), it resizes to fit the card()s specified height. This means, by specifying height = 250 we’ve effectively shrunk the plot’s height from its default of 400 down to about 200 pixels. And, when expanded to full_screen, the plot grows to match the card()’s new size.

card(
  height = 250,
  full_screen = TRUE,
  card_header("A filling plot"),
  card_body(plotly_widget)
)
A filling plot

Most htmlwidgets (e.g., plotly, leaflet, etc) and some other Shiny output bindings (e.g, plotOutput(), imageOutput(), etc) are fill items by default, so this behavior “just works” in those scenarios. And, in some of these situations, it’s helpful to remove card_body()’s padding, which can be done via spacing & alignment utility classes.

card(
  height = 275,
  full_screen = TRUE,
  card_header("A filling map"),
  card_body(
    class = "p-0",
    leaflet_widget
  ),
  card_footer(
    class = "fs-6",
    "Copyright 2023 RStudio, PBC"
  )
)
A filling map

Fill item(s) aren’t limited in how much they grow and shrink, which can be problematic when a card becomes very small. To work around this, consider adding a min_height on the card_body() container. For example, try using the handle on the lower-right portion of this card example to make the card taller/smaller.

This interactive example is a bit contrived in that we’re using CSS resize to demonstrate how to make plots that don’t shrink beyond a certain point, but this concept becomes quite useful when implementing page-level filling layouts (i.e., page_fillable()) with multiple cards.

card(
  height = 300,
  style = "resize:vertical;",
  card_header("Plots that grow but don't shrink"),
  card_body(
    min_height = 250,
    plotly_widget,
    plotly_widget
  )
)
Plots that grow but don't shrink

Troubleshooting fill

As you’ll learn more about in filling layouts, a fill item loses its ability to fill when wrapped in additional UI element that isn’t a fillable container. To fix the situation, use as_fill_carrier() to allow the additional element to carry the potential to fill from the card_body() down to the fill item.

Multiple card_body()

A card() can have multiple card_body()s, which is especially useful for:

  1. Combining both resizable and non-resizable contents (i.e., fill items and non-fill).
  2. Allowing each card_body() to have their own styling (via inline styles and/or utility classes) and resizing limits (e.g., min_height).

For example, when pairing filling output with scrolling content, you may want min_height on the filling output since the scrolling content will force it to shrink:

card(
  height = 375,
  full_screen = TRUE,
  card_header(
    "Filling plot, scrolling description"
  ),
  card_body(
    min_height = 200,
    plotly_widget
  ),
  card_body(
    class = "lead container",
    lorem::ipsum(paragraphs = 10, sentences = 5)
  )
)
Filling plot, scrolling description

Amet blandit faucibus tempor, lacinia nec himenaeos a. Morbi non torquent montes arcu nec, habitant conubia mollis in! Parturient ac varius enim neque turpis: natoque mi turpis: fusce rhoncus. Inceptos consequat tincidunt taciti eros sapien blandit? Malesuada diam erat, cursus, malesuada ad elementum.

Ipsum phasellus placerat sociosqu, morbi habitasse massa mollis varius dictumst vehicula! Pellentesque justo augue euismod at feugiat eleifend leo dictumst. Curabitur dignissim ridiculus mollis lobortis inceptos, facilisis ligula class dictumst. Torquent aliquet dictumst tellus per libero phasellus fusce quisque nulla! Sollicitudin mus consequat eget integer aptent.

Dolor ornare mus est tortor nullam aptent vivamus interdum? Convallis nostra, ultrices, vivamus ante euismod orci. Cras magna ultrices natoque lobortis, lacus at lacus. Sociis montes laoreet mi curae elementum; hendrerit sollicitudin, platea inceptos elementum laoreet nisi. Integer natoque sollicitudin molestie class egestas, est taciti proin erat nascetur placerat convallis.

Lorem habitasse aliquet vitae, suspendisse magna, volutpat taciti ornare vel. Ridiculus ultricies habitasse volutpat, malesuada, tortor ridiculus dictumst platea mauris suscipit: lacinia aenean. Varius nec ridiculus ultrices felis lacinia in litora. Tellus eget class, volutpat sagittis est eget, nascetur malesuada venenatis. Integer urna, purus torquent odio – duis nibh conubia odio?

Consectetur luctus vehicula egestas mattis odio potenti, nostra, justo morbi est sociosqu tempus. Eros eget hendrerit, suspendisse augue sed ad venenatis! Aenean sem tortor interdum mollis integer nunc eros etiam. Senectus cubilia eleifend phasellus blandit sem, vivamus ligula congue pulvinar platea? Facilisi facilisi venenatis metus egestas aptent enim, faucibus ut molestie.

Adipiscing nam lectus inceptos, duis, est massa ad lobortis, cras sociis eleifend? Pretium fringilla et mauris erat, pulvinar: facilisis faucibus volutpat facilisis? Elementum rutrum pulvinar montes – class tempor taciti; nostra elementum dis. Nunc pretium neque, duis ornare gravida. Magna duis hac mattis nunc, sapien nunc, viverra viverra primis proin habitant mauris curabitur.

Ipsum nulla lacus: vestibulum lacinia congue laoreet nec netus gravida ut? Posuere suspendisse purus, cubilia dui nascetur condimentum tempus maecenas. Placerat penatibus natoque proin ullamcorper sociis curae varius condimentum pulvinar montes vehicula sem. Potenti tellus, euismod quisque nisl – quam; vivamus ac venenatis. Malesuada rhoncus bibendum viverra a cubilia sapien elementum.

Adipiscing porttitor hendrerit semper rhoncus fringilla risus sociosqu vehicula nisi? Orci mus sem arcu phasellus tellus integer enim ullamcorper. Penatibus nunc convallis nulla litora ultrices faucibus, facilisis porttitor sociosqu. Lacinia dapibus felis vulputate imperdiet hac sociis dictumst neque luctus sed. Auctor habitasse venenatis arcu dapibus fames, facilisi placerat; integer per vivamus interdum laoreet aliquam?

Dolor et suscipit viverra suspendisse sodales. Et tempus convallis bibendum habitant pellentesque phasellus augue vulputate felis! Lacinia ante interdum senectus conubia faucibus nullam augue lobortis hendrerit. Volutpat luctus eu porttitor ultrices neque massa. Interdum aptent felis penatibus, id fermentum purus sollicitudin varius nisi donec?

Amet taciti nascetur ullamcorper sociis per cursus congue? Lobortis augue, sociis magnis vestibulum orci curabitur, iaculis inceptos. Molestie quisque eu mollis non in tortor aenean, penatibus volutpat placerat. Sollicitudin eget sem; commodo neque lacus massa fermentum penatibus quam, venenatis nascetur sodales? Augue integer mi eu metus magna.

Also, when the content has a fixed size, and should not be allowed to scroll, set fill = FALSE:

card(
  height = 350,
  full_screen = TRUE,
  card_header(
    "Filling plot, short description"
  ),
  plotly_widget,
  card_body(
    fill = FALSE, gap = 0,
    card_title("A subtitle"),
    p(class = "text-muted", "And a caption")
  )
)
Filling plot, short description
A subtitle

And a caption

Multiple columns

As you’ll learn in column-based layouts, layout_column_wrap() is great for multi-column layouts that are responsive and accommodate for filling output. Here we have an equal-width 2-column layout using width = 1/2, but it’s also possible to have varying column widths.

card(
  height = 350,
  full_screen = TRUE,
  card_header("A multi-column filling layout"),
  card_body(
    min_height = 200,
    layout_column_wrap(
      width = 1/2,
      plotOutput("p1"),
      plotOutput("p2")
    )
  ),
  lorem::ipsum(paragraphs = 3, sentences = 5)
)
A multi-column filling layout

Ipsum facilisis mus iaculis, porttitor consequat leo, congue sed imperdiet porta. Dictum eleifend mi integer semper nibh quam non id etiam senectus nunc. A integer arcu condimentum, semper potenti sapien auctor scelerisque facilisis mollis auctor? Imperdiet augue; sollicitudin fames cras egestas dapibus ultricies class. Conubia rhoncus cum lacinia cras lacus, nunc tincidunt odio convallis suscipit hac.

Elit placerat magna vehicula, varius orci commodo malesuada aliquam duis morbi. Mattis vehicula ultrices viverra vitae, aliquam fringilla per semper duis nulla hac! Et ridiculus pulvinar sem phasellus fames hendrerit in hendrerit. Cras laoreet nibh aliquet leo hendrerit eget himenaeos vulputate habitant! Feugiat fermentum leo lacus etiam interdum quam velit ridiculus dapibus facilisi.

Amet scelerisque varius condimentum curae purus neque! Maecenas volutpat laoreet ornare enim a nulla nec aliquam vel. Sem vestibulum posuere, arcu porta elementum dui sapien velit sagittis. Porta tempor class metus bibendum mus pellentesque id consequat. Vestibulum ad massa aliquam venenatis eros, luctus tincidunt inceptos aliquet: hendrerit ligula proin ad facilisis malesuada cum pharetra in, hendrerit porta lobortis nisi torquent.

Multiple cards

layout_column_wrap() is especially nice for laying out multiple cards since each card in a particular row will have the same height (by default). Learn more in column-based layouts.

layout_column_wrap(
  width = 1/2,
  height = 300,
  card(full_screen = TRUE, card_header("A filling plot"), plotly_widget),
  card(full_screen = TRUE, card_header("A filling map"), card_body(class = "p-0", leaflet_widget))
)
A filling plot
A filling map

Multiple tabs

navset_card_tab() and navset_card_pill() make it possible to create cards with multiple tabs or pills. These functions have the same full_screen capabilities as normal card()s as well some other options like title (since there is no natural place for a card_header() to be used). Note that, each nav_panel() object is similar to a card(). That is, if the direct children aren’t already card items (e.g., card_title()), they get implicitly wrapped in a card_body().

library(leaflet)
navset_card_tab(
  height = 450,
  full_screen = TRUE,
  title = "HTML Widgets",
  nav_panel(
    "Plotly",
    card_title("A plotly plot"),
    plotly_widget
  ),
  nav_panel(
    "Leaflet",
    card_title("A leaflet plot"),
    leaflet_widget
  ),
  nav_panel(
    shiny::icon("circle-info"),
    markdown("Learn more about [htmlwidgets](http://www.htmlwidgets.org/)")
  )
)
HTML Widgets
A plotly plot
A leaflet plot

Learn more about htmlwidgets

As you’ll learn more about in sidebar layouts, layout_sidebar() just works when placed inside in a card(). In this case, if you want fill items (e.g., plotly_widget) to still fill the card like we’ve seen before, you’ll need to set fillable = TRUE in layout_sidebar().

card(
  height = 300,
  full_screen = TRUE,
  card_header("A sidebar layout inside a card"),
  layout_sidebar(
    fillable = TRUE,
    sidebar = sidebar(
      actionButton("btn", "A button")
    ),
    plotly_widget
  )
)
A sidebar layout inside a card

Static images

card_image() makes it easy to embed static (i.e., pre-generated) images into a card. Provide a URL to href to make it clickable. In the case of multiple card_image()s, consider laying them out in multiple cards with layout_column_wrap() to produce a grid of clickable thumbnails.

card(
  height = 300,
  full_screen = TRUE,
  card_image(
    file = "shiny-hex.svg",
    href = "https://github.com/rstudio/shiny"
  ),
  card_body(
    fill = FALSE,
    card_title("Shiny for R"),
    p(
      class = "fw-light text-muted",
      "Brought to you by RStudio."
    )
  )
)
Shiny for R

Brought to you by RStudio.

Flexbox

Both card() and card_body() default to fillable = TRUE (that is, they are CSS flexbox containers), which works wonders for facilitating filling outputs, but it also leads to surprising behavior with inline tags (e.g., actionButton(), span(), strings, etc). Specifically, each inline tag is placed on a new line, but in a “normal” layout flow (fillable = FALSE), inline tags render inline.

card(
  card_body(
    fillable = TRUE,
    "Here's some", tags$i("inline"), "text",
    actionButton("btn1", "A button")
  ),
  card_body(
    fillable = FALSE,
    "Here's some", tags$i("inline"), "text",
    actionButton("btn2", "A button")
  )
)
Here's some inline text
Here's some inline text

That said, sometimes working in a flexbox layout is quite useful, even when working with inline tags. Here we leverage flexbox’s gap property to control the spacing between a plot, a (full-width) button, and paragraph. Note that, by using markdown() for the paragraph, it wraps the results in a <p> tag, which means the contents of the paragraph are not longer subject to flexbox layout. If we wanted, we could do something similar to render the actionButton() inline by wrapping it in a div().

card(
  height = 325, full_screen = TRUE,
  card_header("A plot with an action links"),
  card_body(
    class = "gap-2 container",
    plotly_widget,
    actionButton(
      "go_btn", "Action button",
      class = "btn-primary rounded-0"
    ),
    markdown("Here's a _simple_ [hyperlink](https://www.google.com/).")
  )
)
A plot with an action links

Here's a simple hyperlink.

In addition to gap, flexbox has really nice ways of handling otherwise difficult spacing and alignment issues. And, thanks to Bootstrap’s flex utility classes, we can easily opt-in and customize defaults.

card(
  height = 300, full_screen = TRUE,
  card_header(
    class = "d-flex justify-content-between",
    "Centered plot",
    checkboxInput("check", " Check me", TRUE)
  ),
  card_body(
    class = "align-items-center",
    plotOutput("id", width = "75%")
  )
)
Centered plot

Shiny

Since this article is statically rendered, the examples here use statically rendered content/widgets, but the same card() functionality works for dynamically rendered content via Shiny (e.g., plotOutput(), plotlyOutput(), etc).

An additional benefit that comes with using shiny is the ability to use getCurrentOutputInfo() to render new/different content when the output container becomes large enough, which is particularly useful with card(full_screen = T, ...). For example, you may want additional captions/labels when a plot is large, additional controls on a table, etc (see the value boxes article for a clever use of this).

# UI logic
ui <- page_fluid(
  card(
    max_height = 200,
    full_screen = TRUE,
    card_header("A dynamically rendered plot"),
    plotOutput("plot_id")
  )
)

# Server logic
server <- function(input, output, session) {
  output$plot_id <- renderPlot({
    info <- getCurrentOutputInfo()
    if (info$height() > 600) {
      # code for "large" plot
    } else {
      # code for "small" plot
    }
  })
}

shinyApp(ui, server)

Appendix

The following CSS is used to give plotOutput() a background color; it’s necessary here because this documentation page is not actually hooked up to a Shiny app, so we can’t show a real plot.

.shiny-plot-output {
  background-color: #216B7288;
  height: 400px;
  width: 100%;
}